AP®︎/College Environmental science
The nitrogen cycle
How nitrogen is recycled in our biosphere in the nitrogen cycle, including nitrogen fixation.
Want to join the conversation?
- When we breathe in air, do we also breathe in the nitrogen in the atmosphere and do we take in this nitrogen? Or do we just exhale it? Is the only source of nitrogen for humans from our food? :)(19 votes)
- No, we cannot obtain usable nitrogen through breathing. Nitrogen has to be "fixed“ into a usable form first before it is consumed by heterotrophs(16 votes)
- Is there anything else that can capture Nitrogen aside from Bacteria?(7 votes)
- Yes there are. Organisms called Archaea also capture nitrogen and fix them. Hope this helps😁(10 votes)
- If bacteria are the prime fixers of nitrogen, what are some ideas on how the nitrogen was fixed which was used to make protoDNA or protoRNA in pre-bacteria times?(4 votes)
Turns out that lighting can break apart and recombine compounds that were in the early earth to form amino acids. This is most likely what happened back then.
If you are interested in how life started, watch How the Universe Works S04 EP5: The Dawn of Life.
Hope I helped a bit! :)(3 votes)
- Like nitrogen has many advantages, so is there any disadvantage of nitrogen also?(4 votes)
- If nitrogen makes up 72% of air ,then how much of oxygen and carbon makes up air?(3 votes)
- oxygen 20.9476%
Carbon dioxide 0.0314%
- How are amino acids created again? Can someone briefly explain the method?(2 votes)
- Amino acids are organic compounds that combine to form proteins. Amino acids and proteins are the building blocks of life. When proteins are digested or broken down, amino acids are left. The human body uses amino acids to make proteins to help the body Break down food, Grow, repair body tissues and perform other body functions.
hope this helped.(1 vote)
- I get that we can't use the nitrogen we breathe, but are there any large organisms that do?(2 votes)
- On our scale, no. Nitrogen gas in the air is inert and doesn't react easily, so it just exists there. Nitrogen has to be somehow absorbed into water or soil before being used by anything.(2 votes)
- what are the names of bacteria in the nitrogen cycle(2 votes)
- Many heterotrophic bacteria live in the soil and fix significant levels of nitrogen without direct interaction with other organisms. Examples of this type of nitrogen-fixing bacteria include species of Azotobacter, Bacillus, Clostridium, and Klebsiella.
Species of Azospirillum are able to form close associations with several members of the Poaceae (grasses). These bacteria fix appreciable amounts of nitrogen within the rhizosphere of the host plants.
- Whats the role of lightning in the fixation process?(1 vote)
- Lightning allows nitrogen in the air which to turn into nitrates directly, allowing plants to intake it - plants cannot take in nitrogen in the air directly.(3 votes)
- I know this video was made a while ago, but I have a question. If the nitrogen in a body is not completely consumed by bacteria, does it go to the soil or the atmosphere?(2 votes)
- Both- soil and atmosphere. Depending on what state or compound the nitrogen is part of.(1 vote)
- [Voiceover] Nitrogen often gets less attention than carbon or oxygen, but nitrogen is very important to life as well. And like carbon and oxygen, it cycles through our biosphere. Now, one thing that's maybe surprising about nitrogen, if you haven't studied it much, is that it is very, very common in our atmosphere. 78% of our atmosphere is molecular nitrogen, so it's in the form of N2. So this right over here is molecular nitrogen. You have two nitrogen atoms covalently bonded to each other. Now, unlike carbon, which can be directly fixed by plants, in the carbon cycle video we talk about how autotrophs like plants can take light energy and use that to fix carbon from the air into a solid form and store that energy in those carbon-carbon bonds, nitrogen cannot be directly fixed by complex organisms, like plants. Instead, the key actor that fixes the nitrogen from the air, so you have all of these N2 molecules in the air here, the actors here aren't plants, but prokaryotes, like bacteria. So let me draw some soil here. And the bacteria could be in a bunch of different places. But you could have a bacteria in this soil. I'll draw them a little bit bigger so you can see it. Some prokaryotes right over here, there's the bacteria. And certain types of bacteria are capable, and prokaryotes are capable of fixing nitrogen. So what they're able to do, is they're able to take that N2 and turn it into a form that is more usable by complex organisms like plants. So this is the bacteria, right over here. So that's the bacteria. That's this little circular strand of DNA, I could draw other-- I could make it more complicated, but let me just do it like this. Bacteria is able to fix that N2 and take it to ammonia, NH3. And it's this ammonia, it's this ammonia, that is really useful for plants and other complex organisms. So this right over here. So as the plant in the video on the carbon cycle we talk about how plants fix carbon, carbon makes up a large part of organic molecules, but many important organic molecules also need nitrogen. And these are examples of organic molecules that you will find in plants, and you'll find them in many different types of organisms. So this right over here is an amino acid, amino acid, we see the nitrogen right over there. This right over here is our good old friend, ATP, adenosine triphosphate, the quick-store of energy in biological systems. You see the nitrogen in blue right over here. This is the famous DNA, deoxyribonucleic acid. And you see the nitrogens throughout this macro molecule. So nitrogen is essential for life, but the step of fixing that nitrogen that's done by bacteria, which can then produce the ammonia, which is then usable by plants, and then by eating the plants, beings like you and me can get that nitrogen into our systems. Now, it's not just a one-way street. That is, we're just going from the nitrogen in the atmosphere, and it gets fixed by prokaryotes, and then that gets used-- that gets turned into ammonia and gets used by higher organisms. Because eventually all of it would, would get deleted. As an organism dies, as an organism dies, let's say this is a dead organism, it could be a bacteria, but I'll go with a higher organism, a multi-cellular one, this is a dead plant here, I don't want to draw dead animals, it's more morbid. So let's say this is a dead plant there. And when it gets decomposed, and there are many different types of bacteria, even though I might draw them kind of looking the same, let's say this is another bacteria in orange. As these bacteria digest these plants, they're able to, they could take some of the nitrogen and break them down into nitrites and nitrates, these are molecules involving a nitrogen bonded to two or three oxygens, and they can take them back to ammonia. So we can go back, so we can have a bacteria that take us back to ammonia, or eventually by converting the nitrogen into nitrites and nitrates, we could go back we could go back to that molecular nitrogen, that N2. That then gets released back into the atmosphere. So, or it could get, even, you know, it could get stored in other ways as well. But, in general, as you see here, this pattern. That we have these elements that are essential for life. They don't just disappear or form out of nowhere, they're constantly being recycled in our biosphere. And nitrogen doesn't get as much attention as carbon or oxygen, but it is essential for life. In fact, when you look at especially plants and growing plants, and you think about fertilizer. Fertilizer is something that you should think if you add it to a plant, it's going to grow more. So without it, it kind of limits how fast a plant can grow, a lot of fertilizer is going to have nitrogen, and in other video, we're going to talk about phosphorous. And that phosphorous and nitrogen and their availability in the soil, is often a rate-limiting factor for plants. And you know that, because if you add more nitrogen or that phosphorous, it will add more ammonia to that soil, you're going to, the plants are going to grow faster.